It is presently known to form such a segmented flange coupler from a plurality of coupling segments, generally arcuate in shape, which are bolt connected in an end-to-end relationship about the circumference of the pipe. Typically two such coupling segments, of a generally semi-circular shape, are employed. However for large pipe sizes three or more coupling segments may be utilized.
The ends of the coupling segments include bolt receiving apertures for connecting the successive coupling segments together. The coupling segments typically include a key which extends within a circumferential groove of the pipe. Oftentimes the pipe may be somewhat out of round such that the bolt receiving holes of the successive coupling segments will not line up. Accordingly, appreciable force must then be applied to appropriately bring the coupling segments together, as near as possible, to appropriately engage the pipe circumference.
Typically, such prior constructions, for example, the Style 741 segmented pipe coupling available from the Victaulic Company of America, has included radially extending ears at the ends of the coupling segments being bolt connected. The ears must then be engaged with a tool, such as a pliers or channel lock, to bring the ears together such that the bolt can pass through the overlapped apertures for the tight connection of the adjacent coupling segments. Further, it has been experienced that the bolt receiving apertures in such coupling segments must be located with a high degree of accuracy.
Other constructions are also known to bring the adjacent coupling segments into circumferential alignment.
Thiessen, U.S. Pat. No. 3,895,833, provides a flange adapter for use in such a situation. Thiessen's flange adapter includes two or more coupling segments that are connected to each other in end-to-end relationship by means of bolts that are employed to secure the respective coupling segments directly to the flange of the fitting.
Thiessen employs ramp cams on the respective ends of his coupling segments that are interengaged when the coupling segments are assembled onto the grooved pipe. The ramp cams cause circumferential movement of the assembled segmented pipe coupling at the time the bolts are tightened down. This causes the respective flange segments to bottom down on the bottom wall of the groove formed in the pipe, and provide a circumferential alignment between the pipe and the fitting.
However, the provision of such ramp cams carries with it a disadvantage that the flange segments must either be assembled relative to each other prior to the insertion of the traction bolts, with the ramp cams on the respective flange segments interengaged or, the keys of the respective segments must be of lesser width than the width of the pipe groove. If, however, the keys do not engage the side walls of the pipe groove, then, a flexible coupling results, as opposed to a rigid intercoupling of the pipe and the associated fitting.
There is no provision for radial alignment, and hence no guarantee that the flange segments will be truly concentric as related to the longitudinal axis of the assembled coupling, and in turn, as related to the longitudinal axis of the pipe.
Free play of the bolts in the bolting pads of the respective flange segments, will permit the ends of the respective flange segments to be displaced in the radial direction relative to the juxtaposed flange by a distance that is equal to the difference between the diameter of the bolt holes in the respective flange segments and the diameter of the bolts employed for securing the respective segments to each other.
Further, Thiessen's ramp cams, which extend radially of the axis of the coupling, are inoperative to produce any force that acts to move the respective flange segments into concentric relationship relative to the central axis of the coupling.
This can cause problems at the time the flange segments are tightened onto the fitting by means of the bolts if the flange segments at that time are out of concentric alignment. As a consequence they do not bottom down correctly on the bottom wall of the pipe groove, until such time as they are forced into concentric relation by their engagement with the bottom wall of the pipe groove. However, at the time the bolts are being tightened down, to cause the diameter of the flange coupling to decrease, there then exists a considerable frictional restraint against any radial movement of the flange segments relative to each other, with the consequence that the flange segments are not truly concentric with each other. Hence there is no guarantee that the flange segments have in fact bottomed down correctly into full face engagement with the bottom wall of the pipe groove.
If the segments have in fact not bottomed down fully on the bottom wall of the pipe groove, then, the strength of the interconnection is materially affected, as is the probability that a rigid connection has not been effected between the pipe and the fitting by the flange segments. In such a situation, the pressure that the coupling can withstand will be reduced.
Smith U.S. Pat. No. 696,603 discloses a pipe coupler having two pairs of interfitting projections and recesses. One of the pairs is provided for initially locating the adjacent coupling segments during their initial assembly. The other pair is provided to circumferentially align the coupling segments. As was the situation with Thiessen, there is no provision for radial alignment of the adjacent coupling segments. Hence the Smith construction will not automatically provide for the concentric location of the segmented pipe coupling about the pipe.